Today's aircraft are often equipped with separate systems for emergency power supply and cargo fire suppression. For a so-called “total engine flame out” (TEFO) situation or the loss of a main electrical power supply, a ram air turbine for providing emergency power is designated. Ram air turbines are capable for providing sufficient power when the speed of the impinging ram air is sufficient. However, this may be critical in a phase close to touchdown during the landing phase of the aircraft.
For extinguishing or suppression of a fire in a cargo compartment of an aircraft, Halon fire extinguishers were often used. Due to adverse effects of Halon for the ozone layer and as Halon will be limited by authorities, a replacement of Halon is necessary.
In civil aviation, potable water systems are well-known, which use on board water storage tanks for providing the quantity of water used in flight by passengers and crew and lavatories and galleys. It is known to generate potable water on board by means of fuel cells under consumption of hydrogen and oxygen. However, this kind of water generation is directly coupled with the generation of electrical power. Hence, water will only be produced if there is a demand for electric power.
In case air is used as an oxidant, fuel cells deplete the oxygen content of the air when generating water. If the remaining oxygen content in the cathode air is reduced to approximately 12%, this oxygen depleted air is usable for suppressing fire in case of a fire event on board or be used for fuel tank inerting or increasing safety in the fuel system. The depletion of oxygen is directly coupled with the demand for electric power and the stoichiometry in the fuel cell.